The present invention relates to a piston actuation system of a V-type internal combustion engine with a variable compression ratio mechanism, and specifically to the improved arrangement of a multiple-link variable compression ratio mechanism on a crankshaft of a V-type internal combustion engine.
On V-type four-cycle engines, such as V-6 four-cycle engines, in order to shorten the engine""s overall length, adjacent crankpins for at least one pair of cylinders in left and right cylinder banks, for example a crankpin number 1 and a crankpin number 2 are arranged within a span of two adjacent main bearing journals (e.g., a main bearing journal number 1 and a main bearing journal number 2). The adjacent crankpins are often offset from each other. In case of such an offset arrangement of two adjacent crankpins, an axial dimension of each crankpin is shortened by a reinforcing crankshaft web space, as compared to in-line engines. On V-type engines with an offset crankpin arrangement, there are problems of the greatly limited space around the crankpin and insufficient crankshaft strength.
In recent years, there have been proposed and developed various reciprocating piston engines with a variable compression ratio mechanism. Generally, the variable compression ratio mechanism has a plurality of links mechanically linking a crankpin and a piston pin. By varying a condition of restriction of a motion of one link of the links, a compression ratio of the engine changes One such variable compression ratio mechanism has been disclosed in pages 706-711 of the issue for 1997 of the paper xe2x80x9cMTZ Motortechnische Zeitschrift 58, No. 11xe2x80x9d.
On reciprocating piston engines with a relatively complicated variable compression ratio mechanism, it is important to compactly reasonably arrange component parts of the variable compression ratio mechanism. In particular, on V-type reciprocating piston engines, pistons in left and right banks are driven by only one crankshaft, and therefore linkage parts of variable compression ratio mechanisms included in the left and right banks tend to be gathered together closely around the crankshaft. For this reason, a V-type engine with a variable compression ratio mechanism requires a compact and reasonable layout of the linkage parts on the crankshaft.
Accordingly, it is an object of the invention to provide a piston actuation system of a V-type engine with a multiple-link variable compression ratio mechanism, which avoids the aforementioned disadvantages.
It is another object of the invention to provide a piston actuation system of a V-type engine with a multiple-link variable compression ratio mechanism, which is capable of realizing a simple linkage layout, while using a common crankpin to at least one pair of cylinders in left and right cylinder banks.
In order to accomplish the aforementioned and other objects of the present invention, a piston actuation system of a V-type internal combustion engine with a crankshaft and two cylinder banks having at least one pair of cylinders whose centerlines are set at a predetermined bank angle to each other, a pair of pistons slidably disposed in the respective cylinders, comprises a pair of upper links connected to piston pins of the pistons so as to be rotatable relative to the respective piston pins, a pair of lower links connected to the upper links so as to be rotatable relative to the respective upper links, a pair of control links connected at their first ends to the lower links so as to be rotatable relative to the respective lower links, a control mechanism that is connected to the second end of each of the control links to move the second end of each of the control links relative to a body of the engine when changing a compression ratio of the engine, and a crankpin whose axis is eccentric to an axis of the crankshaft and on which a first one of the pair of lower links is rotatably fitted and a crankpin whose axis is eccentric to the axis of the crankshaft and on which the second lower link is rotatably fitted, being coaxially arranged with each other.
According to another aspect of the invention, a piston actuation system of a V-type internal combustion engine with a crankshaft and two cylinder banks having at least one pair of cylinders whose centerlines are set at a predetermined bank angle to each other, a pair of pistons slidably disposed in the respective cylinders, comprises a pair of upper links connected to piston pins of the pistons so as to be rotatable relative to the respective piston pins, a pair of lower links connected to the upper links so as to be rotatable relative to the respective upper links, a pair of control links connected at their first ends to the lower links so as to be rotatable relative to the respective lower links, a control mechanism that is connected to the other end of each of the control links to move the second end of each of the control links relative to a body of the engine when changing a compression ratio of the engine, and the pair of lower links being fitted on an outer periphery of the same crankpin whose axis is eccentric to an axis of the crankshaft.
The other objects and features of this invention will become understood from the following description with reference to the accompanying drawings.